(1) Field of the Invention:
This invention relates to an automobile seat belt system, and especially to a slider drive mechanism and a slide rail for a two-point electric passive seat belt system.
(2) Description of the Related Art:
A passive seat belt system for an automobile serves to automatically restrain an occupant to protect him safely in the event of a vehicular emergency such as a collision when he enters the automobile and also to automatically release him when he egresses from the automobile.
The overall construction of a passive seat belt system is show in FIG. 4. An occupant-restraining webbing 1 is fastened to a slider 2. The slider 2 is driven by a motor 3 via a wire rope, free of illustration, so that the slider 2 may move between a release position and a restraining position along a slide rail 4.
FIG. 6 is a transverse cross-sectional view of a conventional passive slide rail 4. The interior of the slide rail 4 is divided into a wire guide channel 10 and a slider guide channel 11. It has been difficult to reduce the height, i.e., the vertical dimension of the slide rail 4 because the wire guide channel 10 and slider guide channel 11 are located centrally.
FIG. 7 is a transverse cross-sectional view showing a wire rope 8 and the slider 2, both, received in the slide rail 4. If the height of the slider 2 is reduced in order to reduce the height of the slide rail 4, the height L' becomes shorter in FIG. 7. As a result, the reaction forces R'.sub.1, R'.sub.2 which the slide rail 4 produces upon application of a tensile force F (see FIG. 2) to the slider 2 from the webbing 1 (see FIG. 1) become still greater, whereby the friction between the slider 2 and the slide rail 4 increases to give a greater load upon movement of the slider 2 for restraint or release. This significantly affects the time required for the movement of the slider 2, especially, at low temperatures. This leads to the need for a more powerful motor. When a transverse force is applied to the slider 2, forces equal to the reaction forces R'.sub.1, R'.sub.2 are also applied to the slide rail 4 so that the slider 2 tends to undergo more derailing. For these reasons, it has been difficult to simply reduce the height of the slider 2.